Dependency Parsing Flashcards
What is a dependency grammar?
They are structures that are based on grammatical relations that have been defined by linguists.
What type of word order to dependency grammars have?
They have a free word order
What do the edges and nodes represent in a dependency grammar?
The labels for edges are grammatical relations and nodes are words
What do grammatical relations connect?
They connect head and dependent words
What is the type of a grammatical relation called?
Its grammatical function
What type of graph is a dependency tree?
It is a directed graph as the head node can only have arc coming into it
What is a dependency tree made up of?
Vertices = nodes = words or sometimes stems/affixes
Arcs = Grammatical function relationships
How many incoming arcs does the root node have?
None
How many arcs does each vertice have coming into it?
Just one
How many vertices can the root node reach through some path?
The root node has a path to every vertice
What does it mean if an arc is projective?
We say an arc is projective if for a head and all of its dependents, there is a path to connect them all directly.
In the image, is the arc connecting flight and was projective? Why?
The arc is not projective, because even though we can go from ‘flight’ to ‘was’, and from ‘was’ to ‘which’, there is no path to get from ‘flight’ to either ‘this’ or ‘morning’
In the image below, is the arc from ‘was’ to ‘late’ projective?
It is projective, as we can go from ‘was’ to ‘late’, and from ‘late’ we can go to ‘already’ directly
What do older parsing algorithms assume?
They assume that trees are always projective. English based Treebanks are guaranteed to be projective, but in other languages this is not the case and graphs can often include non-projective trees
What Treebanks are used that include dependency graphs?
The Penn Treebank and the Ontonotes dataset
How can we move from Parse-Structures (Constituency Grammars) to Dependency Structures?
We can identify head-dependent structures using head rules, and then we can connect children to heads using a dependency relation